Requirements traceability is intended to ensure continued alignment between stakeholder requirements and system evolution. To be useful, traces must be organized according to some modeling framework. Indeed, several such frameworks have been proposed, mostly based on theoretical considerations or analysis of other literature. This paper, in contrast, follows an empirical approach. Focus groups and interviews conducted in 26 major software development organizations demonstrate a wide range of traceability practices with distinct low-end and high-end users of traceability. From these observations, reference models comprising the most important kinds of traceability links for various development tasks have been synthesized. The resulting models have been validated in case studies and are incorporated in a number of commercial traceability tools. The discussion of the link types and their usage in practice has implications for the design of next-generation traceability methods and tools.

A safety case should present a clear, comprehensive and defensible argument that a system is acceptably safe to operate within a particular context. However, many existing safety cases, in their attempt to manage potentially complex arguments, are poorly structured, presented and understood. This creates problems in developing and maintaining safety cases, and in capturing successful safety arguments for use on future projects. This thesis defines and demonstrates a coherent approach to the development, presentation, maintenance and reuse of the safety arguments within a safety case. This approach is based upon a graphical technique -- the Goal Structuring Notation (GSN) -- and has three strands. Firstly, a method for the use of GSN is defined together with an approach to supporting incremental safety case development. Secondly, the thesis presents a systematic process for the maintenance of a GSN-structured safety argument. Thirdly, the concept of `Safety Case Patterns' is defined as a means of supporting and promoting the reuse of successful safety arguments between safety cases. Examples of the approach are provided throughout. Evaluation of the approach is described through tool implementation, case studies, pilot projects and industrial project applications. Through these activities the approach has been shown to be both a valid and capable tool for safety case management.

Research in design rationale support must confront the fundamental questions of what kinds of design rationale information should be captured, and how rationales can be used to support engineering practice. This paper examines the kinds of information used in design rationale explanations, relating them to the kinds of computational services that can be provided. Implications for the design of software tools for design rationale support are given. The analysis predicts that the "record and replay" paradigm of structured note-taking tools (electronic notebooks, deliberation notes, decision histories) may be inadequate to the task. Instead, we argue for a generative approach in which design rationale explanations are constructed, in response to information requests, from background knowledge and information captured during design. Support services based on the generative paradigm, such as design dependency management and rationale by demonstration, will require more formal integration ...

Knowledge about the rationale for a design---how and why a device is designed as it is---can be valuable, but is difficult to capture in reusable form. This paper presents a view of design knowledge capture and the use of design knowledge for design rationale. We define design rationales as explanations in response to questions about the design. These explanations are generated from knowledge of artifacts and design activities. We characterize design activity in terms of observable changes to design descriptions, and present a theory of design knowledge in the form of an ontology of concepts about design descriptions and operations on them. The theory unifies artifact description and decision-making views of design. Based on the theory, we characterize different methods of acquiring design knowledge and design rationale in the context of integrated design support environments. We then analyze in depth two design knowledge capture techniques: a semiformal representation tool and a model...

Writing scripts (often called "macros") can be helpful for automating repetitive tasks. Scripting facilities for text editors like Emacs and Microsoft Word have been widely used and available. However, for graphical applications, scripting has been tried many times but has never been successful. This is mainly due to the data description problem of determining how to generalize the particular objects selected at demonstration time. Previous systems have mostly tried to solve this using inferencing, but this has a number of problems, including guessing wrong and providing appropriate feedback and control to users. Therefore, the Topaz framework does not use inferencing and instead allows the user to specify how the appropriate objects should be found. This is achieved by recording changes to which objects are selected and searches for objects, so that scripts can be written with respect to the selected object, in the same way as Emacs keyboard macros. Furthermore, all values can be expl...

Capturing design information and decisions is critical to supporting re-use of designs and coordination in engineering teams. Most of this information is currently not recorded at all. In this research we focus on the role of electronic engineering notebooks in the capture, storage and dissemination of design information and decisions, and on their role in integrating and managing design decisions and processes. We propose EEN as a tool ultimately leading towards replacement of traditional paper engineering notebooks and assisting engineers in information related tasks. This paper presents requirements, design and implementation of EEN as well as initial experiment results. Keywords: Electronic Notebooks, Knowledge Acquisition and Access, Collaboration, User Interface Design, Pen-based Computing. 1 Introduction The Knowledge Aided Design (KAD) research at the University of Toronto in collaboration with Spar Aerospace 's Advanced Technology Systems Group is focusing on engineering pro...

In this paper I describe an approach to automated knowledge acquisition in which users specify desired system behavior by constructing justifications of examples. Justifications are explanations of why example behaviors are appropriate in given situations. I analyze the problem of acquiring justifications, showing how current knowledge acquisition techniques are best suited for asking what-questions while justifications are naturally viewed as answers to why-questions. I sketch a new approach for acquiring justifications that transforms why-questions into what-questions, borrowing the sources of power of existing techniques. In this approach, users construct justifications by selecting facts that specify what is relevant in a situation from a space of facts provided by the elicitation tool. Justifications are then used to create operational mappings from situations to intended outcomes. I show how the approach is applied to two different knowledge acquisition problems: the acquisition ...

In this paper Green's (1989) notion of "cognitive dimensions" is used to consider the properties of notations and media for sketching. First, a cultural-cognitive approach to HCI research is briefly outlined which draws on some ideas from "distributed cognition" and Russian psychology. Rather than focussing on the cognitive aspects of an activity or the social aspects (as do cognitive psychology and ethnography, respectively) this approach attempts to describe the artifacts used in an activity in a cognitively and socially relevant way. It is argued that such an approach requires a framework within which to analyse external representations, and that Green's "cognitive dimensions" provide such a framework. The cognitive dimensions framework is described and then used to interpret a study of collaborative idea sketching which used interviewing, observational methods and a questionnaire survey of 128 academics. This analysis resulted in a cohesive and comprehensive characterisati...

In this paper, the "Activity Chain Model", a new design information model necessary for the knowledge medium which realizes "Global Design " is proposed. In order to realize "Global Design", the knowledge medium must provide both intent-capturing and intent-explanation capabilities sufficiently. To provide these capabilities, the "Activity Chain Model " not only integrates both the product and the process based on the activity description, but also introduces a chained structure into the activity. Consequently, this model exceeds the capabilities of conventional media in terms of the range and methods of handling information. For example, this model can capture design process information, including design intent, according to the level of detail of the process information, and the designer's input overhead can be mitigated. The authors implement the model in a computer system called "POET Knowledge Medium". From the results of the evaluation of the "POET Knowledge Medium " through design simulation, the effectiveness of the "Activity Chain Model " was confirmed, not only in the case of capturing and transferring the design intent, but also in reminding the designers themselves of the design process. 1

. Project-specific knowledge is the rationale behind the project data and specifications, including the design decisions that link elements of basic data, design data, project-specifications, domain knowledge, and general knowledge to explain the design. This information should be available in design documentation, but usually it is missing. The paper describes an approach for improving design documentation in which the computer acts as an apprentice to the designer to capture the rationale during the design process. The initial focus of the work is on HVAC (Heating, Ventilation, and Air Conditioning) design. We are using videotape analysis of design sessions along with structured interviews to develop a model of design rationale in this domain. INTRODUCTION The life cycle of the civil engineering facilities can be measured in decades, a long period during which the facility may undergo substantial changes. Moreover, most of the facilities are highly complex and require substantial t...